In Hokkaido, because of only one contaminated car, twins (13) got sick and even a doctor had to give them a medical certificate to tell their symptoms can be from radiation.
Here is how it went.
3.11 Earthquake
3.12 Reactor 1 exploded.
3.14 Reactor 3 exploded. → Their grandparents evacuated to Koriyama shelter by a car called “Minika”
3.17 The grandparents evacuated to Yokohama by leaving the car in Koriyama.
3.29 The grandparents picked up Minika again and moved to Hokkaido. → Their grandchildren, twins, started getting in the car.
May Both of the twins got serious fatigue.
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July
7.28~30 Grandparents went back to Fukushima and picked up the other car of them, called Forester. This car has been left there for 4 months.
8.4 After getting on Forester, Twins got sick and fatigue again.
Early August one of the twins became better but the other one became worse.
8.15 Twins got a medical check for nausea, headache, fatigue, night sweats and anemia.→ Nothing detected from blood test.
8.18 One of the twins started having his right leg hurting and the other one got cramp.
8.30 From the radiator of Minika, they measured 0.9 microSv/h.
Mid September one of the twins started having disturbance in gait.
11.9 Doctor gave them medical certificate.
11.18 They measured 2.6 microSv/h from the frontdeck of Minika.
12.1 From the portion of the dust in the car, they measured 3.03 microSv/h (Gamma + Beta)
They measured 0.62 microSv/h.(Gamma)
12.14 Isotope Research Institute measured Cesium 137 = 3,587 Bq、Cesium 134 = 2,907 Bq from the portion of the dust. → Cesium 134 + 137 = 1,300,000 Bq/Kg
(Source)